Conventionally known as an example of techniques relating to a spectrometer using a terahertz wave is a terahertz-wave spectrometer described in Patent Literature 1. In this terahertz-wave spectrometer, an entrance surface of an internal total reflection prism is integrally provided with a terahertz-wave generator, while an exit surface of the internal total reflection prism is integrally provided with a terahertz-wave detector. Using such an integral prism integrating the internal total reflection prism, terahertz-wave generator, and terahertz-wave detector together is advantageous in that it can detect terahertz waves at high efficiency while reducing the size of the total reflection spectrometer.
An example of detection devices for performing transmission spectrometry which detects the state of a terahertz wave transmitted through an object to be measured is one disclosed in Patent Literature 2. In this detection device, both end faces of a multilayer body formed by holding both sides of a polystyrene sheet with metal sheets are provided with a terahertz-wave generator and a terahertz-wave detector. A void having a rectangular cross section is formed at a center part of the polystyrene sheet, so as to be filled with an object to be measured.